A. Field of the Invention
The present invention relates to novel heterocyclic amides and more particularly relates to heterocyclic amides which are 5-lipoxygenase inhibitors and are useful as anti-inflammatory and anti-allergy agents.
It is well recognized that arachidonic acid and its analogs, unsaturated fatty acids, are the precursors of prostaglandins, thromboxanes, the 5-, 11-, 12- and 15-hydroxyeicosatetraenoic acids (HETEs, DIHETEs, TRIHETES) and hydroperoxyeicosatetraenoic acids (HPETEs) and the leukotrienes, all of which have profound physiological effects. The leukotrienes, which are produced via the 5-lipoxygenase pathway, are the major contributors to the onset of the symptoms of asthma, and mediators for immediate hypersensitivity reactions and inflammation.
Leukotrienes are found in inflammatory exudates and are involved in the process of cellular invasion during inflammation. The term "leukotrienes" is used as a generic term to describe a class of substances, such as slow-reacting substance (SRS) which is an important mediator in asthma and other immediate hypersensitivity reactions. Immunologically generated SRS is usually referred to as slow-reacting substance of anaphylaxis (SRS-A). SRS-A consists of leukotrienes (LT) known as A.sub. 4, C.sub.4, D.sub.4, D.sub.5 and E.sub.4. LTC.sub.4 is at least 100 times more potent than histamine in causing long lasting bronchoconstricting effects. The leukotrienes also increase vascular permeability and cause decreased cardiac output and impaired ventricular contraction. LTB.sub.4 may be an important mediator of inflammation in inflammatory bowel disease.
Chemotaxis is a reaction by which the direction of migration of cells is determined by substances in their environment. It is one of the maior processes bringing leukocytes from the blood to an inflammatory site, whether the inflammation is caused by an infectious agent, allergic challenge, or other pro-inflammatory stimuli. LTB.sub.4 is not only chemotactic for neutrophils and monocytes, but is also highly active in stimulating eosinophil locomotion. The infiltration of eosinophils is one of the histologic features of a variety of allergic reactions.
With the exception of benoxaprofen, which has 5-lipoxygenase inhibition activity, aspirin and the other non-steroidal anti-inflammatory agents (NSAIDs) such as indomethacin, ibuprofen, fenoprofen, and the like, inhibit the synthesis of prostaglandins via the cyclooxygenase pathway of arachidonic acid. These prostaglandin synthetase inhibitors generally exhibit anti-inflammatory, anti-pyretic and analgesic activity, and are widely used in the treatment of arthritis. The non-steroidal anti-inflammatory agents can lead to the formation of additional pro-inflammatory derivatives of arachidonic acid produced through the 5-lipoxygenase pathway which play a role in immediate hypersensitivity reactions and also have pronounced pro-inflammatory effects. Administration of the NSAIDs alone can produce allergic reactions including bronchospastic reactivity; skin rashes; syndrome of abdominal pain, fever, chills, nausea and vomiting, and anaphylaxis. For this reason, aspirin and the other non-steroidal anti-inflammatory agents (NSAIDs) are generally contraindicated for patients suffering from asthma or who have previously exhibited allergic sensitivity to aspirin or other NSAIDs.
Prior to the recognition of the arachidonic acid cascade and the significance and interaction of the 5-lipoxygenase and other arachidonic acid cascade conversion products in allergic reactions and inflammation, the search for effective therapeutic agents was based primarily on those agents which treated the symptoms of allergy and inflammation. There has since been effort to develop new drugs which selectively block the formation of the mediators of these conditions, and the present invention provides heterocyclic amides which are metabolically stable inhibitors of the 5-lipoxygenase pathway and are useful in the treatment of asthma and other allergy and hypersensitivity reactions, and many types of inflammation.
To date, benoxaprofen has been the only commercial anti-inflammatory agent which has 5-lipoxygenase inhibition activity. Prior to its withdrawal from the market because of untoward side effects, benoxaprofen was considered to represent a significant advance in the treatment of crippling arthritis and psoriasis. Thus, there remains a longstanding need for agents which block the mechanisms responsible for inflammation and allergic reactions, and which can be safely employed to treat, for example, arthritis, asthma, psoriasis and other dermatoses, allergic reactions and other 5-lipoxygenase mediated conditions. A need also exists for agents which can be administered with the inhibitors of other lipoxygenase enzymes, e.g. cyclooxygenase, to mitigate their side effects and support their desirable medicinal properties.
See Bengt Samuelson, "Leukotrienes: Mediators of Immediate Hypersensitivity Reactions and Inflammation", Science, Vol. 220, pp. 568-575 (May 1983); Michael K. Bach, "Inhibitors of Leukotriene Synthesis and Action", The Leukotrienes, Chemistry and Biology, pp 163-194 (Academic Press, Inc., 1984); C. W. Lee et al., "Human Biology and Immunoreactivity of Leukotrienes", Advances in Inflammation Research, Volume 6, pp 219-225 (Raven Press, New York, 1984); Editorial, "Leukotrienes and other Lipoxygenase Products in the Pathegonesis and Therapy of Psoriasis and Dermatoses", Arch. Dermatol., Vol. 119, pp 541-547 (July, 1983); Robert A. Lewis et al., "A Review of Recent Contributions on Biologically Active Products of Arachidonate Conversion", Int. J. Immunopharmac., Vol. 4, No. 2, pp 85-90 (1982); Michael K. Bach, Biochemical Pharmacology, Vol. 23, No. 4, pp 515-521 (1984); E. L. Becker, Chemotactic Factors of Inflammation, pp 223-225 (Eliver Science Publishers B. V., Amsterdam, 1983); P. Sharon and W. F. Stenson, Gastroenterology, Vol. 84, 454 (1984); and M. W. Musch, et al., Science, Vol. 217, 1255 (1982).
The present invention provides compounds which block the 5-lipoxygenase pathway of the arachidonic acid cascade, block the formation of the leukotrienes therefore responsible for the allergy and inflammation, and hence and represent a new class of therapeutic agents which are useful in the treatment of allergic and hypersensitivity reactions and inflammation, alone, or in combination with other oxygenase inhibitors such as the non-steroidal anti-inflammatory agents (cyclooxygenase inhibitors).